How I Use It
We use Code.org as an introduction to block-based programming for 3rd and 4th grade students. It is the perfect tool to use in advance of Scratch. We have 3rd grade students do Course 2, and 4th grade students do Course 3.
Code.org is set up very well, using levels and stages. The introductory videos to each level are great for students, just make sure they have headphones for the videos. The variety of levels is great, and students enjoy switching games/characters/challenges.
One issue I have is that when completing a stage (puzzle) with too many blocks, the program allows you to move on without correcting the misuse of blocks. In this way, students sometimes guess and are able to move on without understanding their mistake.